Our furnace fan has been surging, fast, then slow, then fast Intermittently. Bill came out, but the furnace was not doing it at the time. I realize how difficult intermittent issues are to fix. Rather then throw parts at the issue hoping to fix it, Bill checked everything thoroughly and was honest that he did not find an issue. He stated that if it happened again he would come back out and waive the truck trip.
Everyone at Sal's is excellent, from the people answering the phone to the techs that come out.